The present invention relates generally to a fuel supply apparatus for an engine. More specifically, the invention relates to a fuel supply apparatus for an internal combustion engine, which is capable of effectively reducing the pressure pulsation of fuel while injectors for injecting a fuel open and close.
A typical fuel supply apparatus for an internal combustion engine for an automobile is designed to pump out a fuel to an injector via a fuel tube and to inject an appropriate amount of fuel into an intake manifold of the engine from the injector.
Conventionally, there is widely used a return type fuel supply system provided with a pressure regulator for regulating the quantity of a fuel injected from the injectors with opening and closing motion and a return tube for returning excessive fuel to a tank. In recent years, a returnless type fuel supply system requiring no return tube is put to practical use.
FIG. 6 shows a returnless type fuel supply system. In this figure, reference number 1 denotes a fuel tank. A fuel delivery rail 2 is connected to a fuel tube 4. A plurality of injectors 5 are attached to the fuel delivery rail 2.
In the returnless type fuel supply system of this type, it is known that there is a disadvantage in that a fuel pressure pulsation remarkably occurs in the fuel delivery pipe 2 and the fuel tube 4 every time the injectors 5 open and close. There is a problem in that vibrations due to the fuel pressure pulsation are transmitted as noises to the inside of a car from the underfloor of a chassis through fuel tubes. For that reason, in order to reduce the fuel pressure pulsation, there are proposed various improvements that a damper is connected to the fuel tube.
In a conventional returnless type fuel supply system, in order to reduce the fuel pressure pulsation, the fuel tube includes the damper for damping the pulsation. In addition, Japanese Patent Laid-Open No. 1999-2164 discloses a technique wherein a delivery rail having a body formed of a pressed sheet metal of 0.8 mm or more in thickness, and the rigidity and content volume of the delivery rail are set in predetermined ranges so that the pulsation resonance cycle of a fuel piping system is an idling cycle or less, thereby reducing the fuel pressure pulsation.
In the prior art disclosed in the above described Japanese Patent Laid-Open No. 1999-2164, although there is an advantage in that it is not required to use any dampers, it is required to increase the volume of the fuel piping system in order to reduce the pulsation.
However, there are some cases where it is difficult to increase the volume of the fuel piping system in a very narrow limited space for engine room in order to only reduce the fuel pressure pulsation. In addition, this is not a reasonable countermeasure against reducing the fuel pressure pulsation.
It is therefore an object of the present invention to eliminate the above described problems in the prior art and to provide a fuel supply apparatus for an engine, which is capable of effectively reducing the fuel pressure pulsation occurred by the injectors opening and closing, by using an inexpensive means and without increasing the volume of a fuel piping system.
In order to accomplish this object, there is provided a fuel supply apparatus for an engine for supplying a fuel, which is pumped out by means of a pump from a fuel tank to an engine, said fuel supply apparatus comprises a plurality of injectors for injecting the fuel to an intake manifold of the engine; a delivery rail, to which the plurality of injectors are attached, for distributing the fuel to each of the injectors; and a fuel tube for introducing the fuel, which is delivered forcedly by means of said pump, to the delivery rail, wherein a body portion of the delivery rail has side portions having different areas, and an orifice portion which is open on the largest side portion of the all side portions and to which an end portion of the fuel tube is connected.
According to the present invention, it is possible to effectively reduce the fuel pressure pulsation in the fuel tube by the injectors opening and closing, by an inexpensive tube or the like and without increasing the volume of a fuel piping system.